Idingender
Idingender is an umbrella term for all genders that are fluid in nature. In being used as an identity on its own, idingender can also be used to refer to either a gender that is not fully defined, but is definitely fluid, or a gender in which fluidity is a defining feature.
The fluctuating counterpart is uxingender; genders that are both idingenders and uxingenders are classified as fluvarilian.
For a comprehensive list of genders under the idingender umbrella, please see Category:Idingender.
Etymology
"Idin" originates from the phrase fluid in nature, using the bolded fragments of each word.